The overall objective of the project is to determine whether or not endogenous secretin plays a physiological role in normal insulin and glucose regulation. We have been able to show that intraduodenal administration of HCl raises secretin and insulin concentrations in the portal blood of dogs. We are presently trying to obtain similar information on humans. Furthermore, we plan to continue our investigations on the nature of the 3 different molecular species of immunoreactive secretin that were isolated from human, canine and porcine duodenal tissues. In addition we will try to demonstrate the presence of secretin heterogeneity in serum. BIBLIOGRAPHIC RERERENCES: Boden, G., Essa, N. and Owen, O.E.: Effects of intraduodenal amino acids, fatty acids and sugars on secretin concentrations. Gastroenterology 68:722-727, 1975. Fisher, R.S., Boden, G.: Reversibility of pyloric sphincter dysfunction in gastric ulcer. Gastroenterology, Sept., l975. In Press.